Coccidiostats: Ionophores and Chemical Anticoccidials, Programmes and Withdrawal

Coccidiostats are feed additives that act against Eimeria, the coccidian parasites of the gut, and in the EU they form category 5 "coccidiostats and histomonostats" of Regulation (EC) No 1831/2003, where the register lists polyether and synthetic substances. Each EU entry names one holder and fixes the animal category, the maximum age, the content per kg complete feed (12 % moisture) and the withdrawal period. For chickens for fattening the contents run from 1 mg/kg (diclazuril 51771) to 125 mg/kg (amprolium 51777), and four implementing regulations adopted in 2026 set new conditions for monensin, narasin, diclazuril and the first narasin + diclazuril combination.

In the US the same substances, called anticoccidials or anticoccidial drugs, are medicated-feed drugs under 21 CFR 558, sold over the counter as Category I or Category II articles. Among the five feed additive categories, coccidiostats are the only one with no functional groups, and no histomonostat is listed in it today. Choice follows the animal category named in the act, the programme slot, the EFSA margin of safety and the carry-over risk in the mill, while withdrawal runs from 0 to 5 days in the EU and from none to 7 days in the US.

Every value on this page is compiled from the EU authorising acts, the EU Register of Feed Additives, EFSA opinions, the eCFR and named peer-reviewed studies, checked on 3 November 2026; see the methodology.

What Is a Coccidiostat?#

A coccidiostat is a substance added to feed to stop the development of coccidia in the gut, authorised in the EU as a category 5 feed additive and approved in the US as a medicated-feed drug. EU law defines a feed additive as a substance, micro-organism or preparation, other than feed material and premixtures, intentionally added to feed or water to perform one or more listed functions (Article 2(2)(a) of Regulation (EC) No 1831/2003). Coccidiosis vaccines belong to a different legal class: they are veterinary medicinal products, not feed additives.

EU category 5 and the US medicated-feed classification#

In the EU, coccidiostats and histomonostats are the fifth additive category of Regulation (EC) No 1831/2003 (Article 6(1)(e)), with no functional groups below it. Every category 5 authorisation is holder-bound: the act names one company, one trade name and one identification number, such as 51701 for Coxidin (Huvepharma N.V.) under Implementing Regulation (EU) 2026/532. Article 11(1) asked the Commission for a report before 1 January 2008 with a view to phasing coccidiostats out by 31 December 2012. No phase-out was adopted, and acts such as 2024/2389, 2026/532, 2026/1860 and 2026/2086 have since set new ten-year conditions.

In the US, coccidiostats are approved animal drugs used in medicated feed under 21 CFR 558, and 21 CFR 558.4 sorts them into Category I and Category II. The category decides which mill may handle the concentrated Type A article, not whether a prescription is needed: no coccidiostat needs a veterinary feed directive.

No histomonostat appears in category 5 of the EU Register (checked 3 November 2026); nifursol was the last one. The polyether coccidiostats are antibiotics by origin, yet their legal path differs from that of antibiotic growth promoters. Article 11(2) let the other antibiotic growth promoters be marketed only until 31 December 2005 and deleted them from 1 January 2006, while monensin sodium and salinomycin sodium remain coccidiostats.

The parasite problem coccidiostats address#

Coccidiosis cost the chicken industry an estimated GBP 10.4 billion worldwide at 2016 prices (range 7.7 to 13.0 billion), about GBP 0.16 per bird produced, according to Blake and colleagues (Veterinary Research, 2020). The same study put the cost in the United Kingdom at GBP 99.2 million in 2016. The losses come from seven Eimeria species of chickens, of which E. brunetti, E. tenella and E. necatrix are the most pathogenic (Mesa-Pineda and colleagues, 2021).

A coccidiostat addresses this problem through the feed of healthy flocks, inside the limits of its authorisation. EU feed additives may not claim to prevent, treat or cure disease (Article 13(3) of Regulation (EC) No 1831/2003), so each act states animal categories, contents and conditions of use rather than a therapeutic effect.

Member Table: Coccidiostat Substances, Combinations and Topic Pages#

The member table lists the coccidiostat substances by chemical family, polyethers first, then the synthetic compounds and the fixed combinations, with EU entry, categories and content, status, US section and withdrawal side by side.

EU contents are mg/kg complete feed (12 % moisture), either a legal minimum and maximum or one fixed value; US levels are approved levels in g/ton under 21 CFR 558 and are not converted. Programmes and carry-over follow coccidiostats through a flock's life and out of other feed.

How Do Coccidiostats Work?#

Coccidiostats work in two ways: fermentation-derived polyethers carry cations across the parasite membrane and collapse its ion gradients, while synthetic compounds block specific metabolic steps such as mitochondrial respiration or thiamine uptake. Polyethers hit the extracellular sporozoites and merozoites, and synthetic compounds generally act inside the cell.

Fermentation-derived polyethers and cation transport#

Polyether coccidiostats form lipid-soluble complexes with sodium and potassium, and lasalocid also with divalent cations, so the sporozoite loses its ion balance. Mesa-Pineda and colleagues (2021, after Peek and Landman) sort the six feed polyethers into the three classes below.

• Monovalent polyethers: monensin, narasin and salinomycin
• Monovalent glycoside polyethers: maduramicin and semduramicin
• Divalent polyether: lasalocid

Polyethers let some oocysts leak through, so birds on medicated feed still develop immunity to Eimeria, and programmes prefer them in grower and finisher feed. Monensin, the first of the class, was introduced in the US in July 1971 (Chapman, Jeffers and Williams, 2010). In ruminants the same compounds shift rumen fermentation, and equine exposure is the main hazard of the class.

Synthetic compounds with mitochondrial, thiamine and unknown targets#

Synthetic coccidiostats hit defined targets: decoquinate and clopidol block mitochondrial electron transport, amprolium blocks thiamine uptake, and the targets of diclazuril, halofuginone, nicarbazin and robenidine remain unknown or multiple. Clopidol and zoalene (dinitolmide) hold US sections only and have no EU Register entry.

Synthetic compounds suppress oocyst output strongly, which also limits the development of immunity. Programmes use them in starter feeds and as clean-up products, and for limited periods, since resistance develops quickly. Noack and colleagues (2019, after Chapman 1997) date the first field resistance to nicarbazin and amprolium in 1964, clopidol in 1969, decoquinate in 1970, robenidine in 1974, halofuginone in 1986 and diclazuril in 1994. Two synthetic entries also carry laying-bird and breeder exclusions that a mill checks before use: nicarbazin and halofuginone.

What EFSA opinions and reviews show#

Every EU coccidiostat dossier needs at least three long-term efficacy studies (Regulation (EC) No 429/2008), and EFSA set margins of safety as narrow as about 1.3 for halofuginone in chickens and none for lasalocid at 90 mg/kg. These margins compare the tolerated content with the authorised maximum.

Reviews describe a class under pressure from resistance. Noack, Chapman and Selzer (Parasitology Research, 2019) report resistance for every anticoccidial in use and no new drug in either family for decades; field resistance followed introduction within 1 to 11 years, for example monensin in 1971 and 1974 and salinomycin in 1983 and 1984. Peek and Landman (Veterinary Quarterly, 2011) conclude that rotation and shuttle programmes have not solved resistance and that plant extracts, prebiotics and probiotics give inconsistent results, so drug-free coccidiosis control rests mainly on live vaccines; vaccines and natural options are weighed under coccidiosis control in poultry.

The pooled effect sizes in this group concern monensin in cattle, a US use with no EU counterpart. In the meta-analysis by Duffield, Rabiee and Lean (2008), covering 77 trials and 9,677 dairy cows, milk yield rose by 0.7 kg/day, dry matter intake fell by 0.3 kg/day and milk production efficiency rose by 2.5 %. In the beef meta-analysis by Duffield, Merrill and Bagg (Journal of Animal Science, 2012), feed efficiency rose by 6.4 % at a mean 28.1 mg/kg DM, but only by 2.5 to 3.5 % in the last two decades, with intake down 3 % and daily gain up 2.5 %.

Choosing by Mode of Action, Safety Margin and Mill Risk#

Choose a coccidiostat by the animal category its act names, the programme slot, the season, the resistance history of the farm and the risk of carry-over in the mill. The table sets each criterion against what to check and the values that apply.

Programmes combine these criteria over a flock's life: shuttle programmes change product between starter and grower feed within one flock, while rotation changes product between flocks, and two polyethers of the same class give no resistance benefit. Coccidiosis vaccines are the main alternative, and alternating vaccinated with medicated flocks introduces drug-sensitive Eimeria, a practice proposed to restore drug sensitivity (Chapman and Jeffers, 2014). Coccidiostats are feed additives in the EU and medicated-feed drugs in the US, while vaccines are veterinary medicinal products; the trade-off is set out in coccidiostats vs coccidiosis vaccines.

Selection by Species and Diet#

Species decides the choice, because the EU authorises each coccidiostat per animal category and maximum age: most entries name chickens for fattening, fewer name turkeys, game birds or rabbits, and none of the entries in the member table names cattle, sheep, goats or laying hens. The table lists the EU entries and US sections per species.

Coccidiostats for broilers and chickens reared for laying#

Chickens for fattening have the widest choice: most EU entries in the member table name them, and each US section in the member table sets a broiler level in g/ton. The polyether contents run from 20 to 25 mg/kg for semduramicin 51773 to 100 to 120 mg/kg for monensin 51701, salinomycin 51766 carries a zero-day withdrawal, and the 2026 entry Interban 51778 (Elanco GmbH, Implementing Regulation (EU) 2026/2061) is the first EU combination of a polyether with diclazuril, fixed at 50 + 1 mg/kg.

Chickens reared for laying appear in fewer entries and always with a maximum age or a fixed content: monensin 51701 to 16 weeks, salinomycin 51766 at 50 mg/kg to 12 weeks, diclazuril 51771 to 16 weeks and 51775 to 12 weeks, plus amprolium 51777 and Interban 51778. Implementing Regulation (EU) 2023/1172 denied lasalocid for chickens reared for laying, and the 51763 entry names chickens for fattening only. In the US, salinomycin (21 CFR 558.550), clopidol (558.175) and zoalene (558.680) also name replacement chickens.

Turkeys, game birds and rabbits#

Turkeys up to 16 weeks can receive monensin 51701 at 60 to 100 mg/kg and halofuginone 51764 up to 12 weeks at 2 to 3 mg/kg; the turkey and game-bird lasalocid entries and the rabbit diclazuril entry carry the register status given in the member table. Lasalocid 5 1 763 (Zoetis Belgium SA) sets 75 to 125 mg/kg with a 5-day withdrawal for turkeys to 16 weeks and for pheasants, guinea fowl, quails and partridges except laying birds.

Rabbits appear only in diclazuril 51775 under Implementing Regulation (EU) 2015/1417 (1 mg/kg, 2-day withdrawal); Implementing Regulation (EU) 2023/2594 denied the robenidine renewal for rabbits. In the US, diclazuril (558.205) and halofuginone (558.265) name growing turkeys, lasalocid (558.311) names chukar partridges and rabbits at 113 g/ton, and zoalene (558.680) names growing turkeys at 113.5 to 170.3 g/ton.

Cattle, calves, sheep and goats: US feed approvals only#

None of the EU entries in the member table names a ruminant, while the US approves monensin, lasalocid, decoquinate and amprolium in cattle feed and monensin for confined goats. Monensin is not authorised in the EU as a feed additive for ruminants, and decoquinate 51756i and 51756ii carry no EU authorisation for calves, sheep or goats.

Each US section sets its own ruminant level. Monensin under 21 CFR 558.355 runs from 5 to 40 g/ton for feedlot cattle (50 to 480 mg/head/day), 11 to 22 g/ton of total mixed ration for dairy cows and 20 g/ton for confined goats, and it is not for veal calves or lactating goats. Lasalocid under 558.311 runs from 10 to 30 g/ton for feedlot cattle and 20 to 30 g/ton for confined sheep. Decoquinate under 558.195 is fed at 0.5 mg/kg body weight per day for at least 28 days to cattle, including calves, and to young sheep and goats, but not to lactating dairy animals. Amprolium under 558.55 is fed to calves at 5 mg/kg body weight per day for 21 days, with a 24-hour withdrawal.

Laying hens, horses, dogs and other non-target animals#

No coccidiostat is authorised in the EU for laying hens, and the acts and US labels warn against feeding several of them to horses, turkeys or birds producing eggs for food. EU entries name at most chickens reared for laying up to a stated age. The US differs for one substance: 21 CFR 558.55 approves amprolium for laying chickens at 113.5 g/ton. The salinomycin label (558.550) reads "May be fatal if accidentally fed to adult turkeys or horses", and the monensin label (558.355) states that it is fatal to horses.

Horses are the most sensitive species: the acute oral LD50 is 1 to 3 mg/kg bw for monensin, 0.8 for narasin and 0.6 for salinomycin, against 40 to 214 mg/kg bw in chickens (Ekinci and colleagues, 2023, review). Pet food has caused field cases, with lasalocid in dog food behind a paralytic syndrome (Safran and colleagues, 1993) and salinomycin in dry cat food behind the 1996 Dutch outbreak (van der Linde-Sipman and colleagues, 1999). EFSA's contaminants panel found the risk at 2, 5 and 10 % cross-contamination negligible except for salinomycin above 2 % and monensin above 5 % in horses (Dorne and colleagues, 2013).

Dosing Logic: Fixed Contents, Legal Ranges and US Approved Levels#

Coccidiostat doses are legal contents, not recommendations: some acts fix one value (lasalocid 90 mg/kg, robenidine 36 mg/kg), others set a minimum and maximum (salinomycin 50 to 70 mg/kg), and the US sets approved levels in g/ton under 21 CFR 558. The table pairs each EU content for chickens for fattening with its basis, the EFSA margin of safety and the US broiler level.

A fixed content is both floor and ceiling, a range lets the mill choose within it, and the EFSA margin shows how far the ceiling sits from the highest tolerated level. A salinomycin margin of 1.7 leaves little room for mixing error, and for lasalocid 51763, monensin 51701 at its new maximum and Interban 51778 EFSA established no margin at all, against about 11 for diclazuril. EU contents are per kg complete feed (12 % moisture), while US levels are per short ton of feed, where 1 g/ton equals 1.1 mg/kg; the table keeps both in their own units. In the US, 21 CFR 558.3 also caps a Type B medicated feed at 200 times the highest continuous use level for Category I drugs and 100 times for Category II.

Regulation Summary: EU Category 5 Authorisations and US Medicated-Feed Status#

In the EU a coccidiostat may be sold only under a holder-bound category 5 authorisation, while in the US it is an approved animal drug used in medicated feed under 21 CFR 558. The EU side runs on dated acts and register entries, and the US side on sections, drug categories and mill licences.

EU category 5 entries, expiry and renewal status#

Four implementing regulations adopted in 2026 set EU coccidiostat conditions: 2026/532 (Coxidin, renewal), 2026/1860 (Monteban G100, new authorisation replacing the 2004 act), 2026/2061 (Interban, new) and 2026/2086 (Clinacox, renewal). Implementing Regulation (EU) 2026/532 cut the monensin maximum for chickens from 125 to 120 mg/kg, lets old-label additive and premixtures labelled before 2026-10-01 and compound feed labelled before 2027-04-01 be used up, and requires EU field resistance monitoring from 2031-04-01. How renewal applications under Article 14 work is explained under EU feed additive regulation.

Older entries carry a status rather than a running date. For narasin + nicarbazin 51772 (Maxiban G160), printed expiry 2020-10-28; the EU Register records a renewal application and still lists the entry pending the Commission decision (Article 14 of Regulation (EC) No 1831/2003), and the same register note applies to lasalocid 5 1 763 and to the 2015 diclazuril 51775 acts. Monensin E 757 (Elancoban, Regulation (EC) No 1356/2004) has a printed expiry of 2014-07-30 and nicarbazin 5 1 774 (Regulation (EU) No 875/2010) one of 2020-10-26; for both, the EU Register records an application under Article 10(2) of Regulation (EC) No 1831/2003 and still lists the entry pending the Commission decision. Maduramicin's act, Implementing Regulation (EU) No 388/2011, set 5 to 6 mg/kg for chickens for fattening with a printed expiry of 2021-05-10.

Great Britain keeps its own register. The Food Standards Agency list downloaded on 3 November 2026 shows Coxiril, Sacox, Monimax, Robenz, Deccox and Avatec for turkeys and game birds as "Authorised", Elancoban, Monteban, Aviax, nicarbazin, halofuginone and Avatec for chickens as "Authorised - Article 10", and Cygro 10G as "Revoked".

US status: Category I and II medicated articles, no VFD#

In the US, coccidiostats are over-the-counter medicated-feed drugs: Category I articles can be used by any feed mill, while a medicated feed mill licence is needed to make Type B or Type C feed from a Category II Type A article. Under 21 CFR 558.4 the two groups are listed below.

• Category I: amprolium with ethopabate, decoquinate, diclazuril, lasalocid, monensin, narasin, narasin with nicarbazin, salinomycin, semduramicin and zoalene
• Category II: amprolium, clopidol, halofuginone, maduramicin, nicarbazin and robenidine

US withdrawal runs from none to 7 days: halofuginone needs 4 days for broilers and 7 for turkeys, robenidine, maduramicin and clopidol (at 227 g/ton) need 5 days, and nicarbazin needs 4 days up to 113.5 g/ton and 5 above. No withdrawal is listed for monensin, lasalocid, salinomycin, narasin, semduramicin, diclazuril, decoquinate or zoalene. None of these drugs is a VFD drug, so feed containing them is sold without a veterinary feed directive. Assay tolerances apply as well; for example, a monensin Type A article must assay at 85 to 115 % of label and a poultry Type C feed at 75 to 125 %.

Use conditions in the acts: no blending, laying-bird limits, labels#

An EU coccidiostat may not be mixed with another coccidiostat unless its act authorises the combination, as for narasin with nicarbazin, monensin with nicarbazin and narasin with diclazuril. Nicarbazin 5 1 774 may be mixed only with narasin (Regulation (EU) No 875/2010), and the combinations reach the market as fixed products under their own identification numbers, 51772, 51776 and 51778, never as two coccidiostats blended by a mill. Annex III of Regulation (EC) No 1831/2003 requires the label to show the expiry date of the guarantee or storage life, the directions for use and the concentration.

Laying birds are protected through the carry-over rules as well as the acts. Directive 2002/32/EC Annex I Section VII, as replaced by Regulation (EU) No 574/2011, sets maximum carry-over levels of coccidiostats in non-target feed, and sensitive compound feed always includes laying birds; Regulation (EC) No 124/2009 sets matching limits in food. A premixture for feed in which the coccidiostat is not authorised may not cause more than 50 % of the compound-feed carry-over maximum.

Sourcing Checklist for Coccidiostat Premixes#

Source a coccidiostat in seven checks, from the identification number and holder on the label to the analysis of the finished feed. The checks follow the order in which a buyer meets them.

1. Match the identification number, holder and animal category on the label to the act, for example 51766 (Huvepharma NV) for chickens for fattening and chickens reared for laying to 12 weeks.
2. Check the status wording: a dated act running to 2036 and a printed expiry with a register note are different statuses.
3. Confirm the US section, Category I or II and, for Category II, the medicated feed mill licence.
4. Compare the active content (10, 12, 20 or 25 %), the carrier and the form, because offers differ on all three.
5. Plan batch sequencing and flushing against the carry-over maxima for non-target feed.
6. Ask for FAMI-QS or GMP+ certification, the transport class and the registration in the destination country.
7. Ask which method the certificate of analysis uses: EN ISO 14183 for polyethers in premixtures and feed, EN 17299 (LC-MS/MS) for compound feed and carry-over, or the HPLC-UV method of Regulation (EC) No 152/2009 for diclazuril.

Holder exclusivity also shapes offers, since each category 5 identification number belongs to one holder. Implementing Regulation (EU) 2025/1419 moved Deccox, Avi-Deccox 60G, Robenz 66G and Avatec 150 G for chickens from Zoetis Belgium S.A. to Phibro Animal Health SA, so a buyer should check that the holder on the label matches the current act.

Coccidiostat Questions#

Three questions about coccidiostats come up in purchasing and compliance discussions.

Are coccidiostats antibiotics?#

Polyether coccidiostats are antibiotics by origin but are not used in human medicine and are not on the WHO list of medically important antimicrobials, while synthetic coccidiostats such as diclazuril, decoquinate and amprolium are chemically synthesised rather than fermentation products. Noack and colleagues (2019) make the WHO point. In EU law the polyethers stayed in category 5 when the other antibiotic growth promoters left the register.

Is a coccidiostat in feed a treatment for coccidiosis?#

No: an EU coccidiostat is authorised for use in the feed of named animal categories at set contents, and EU additives may not claim to treat disease; oral and water treatments are veterinary medicines outside feed. In the US, oral amprolium forms fall under 21 CFR 520.100 as veterinary drugs, separate from the medicated-feed section 558.55. Treatment of sick animals is a veterinary decision, not a feed formulation question.

What side effects do coccidiostats have?#

The documented side effects are toxic interactions with tiamulin, heat-stress mortality with nicarbazin and narrow safety margins at the maximum content. Polyethers interact toxically with tiamulin, erythromycin, chloramphenicol and certain sulfonamides (Noack and colleagues, 2019). In one trial by Long, Johnson and McKenzie (1988), nicarbazin at 125 ppm raised heat-stress mortality in broilers, and narasin with nicarbazin at 50/50 reduced it by 15 to 20 %; nicarbazin carried into layer feed also bleaches eggs and mottles yolks.

Clays sold as mycotoxin binders interact too. Under the bentonite act, Implementing Regulation (EU) No 1060/2013, coccidiostats other than robenidine are contraindicated in poultry above 5 000 mg/kg bentonite and robenidine is to be avoided, and US labels exclude bentonite with amprolium, decoquinate and robenidine; the bentonite limits are on the mycotoxin binders page.